Barton thinks highly of himself and claims to write about the common man and for the common man, when in truth he knows very little about the "common man" (he never listens - and he thinks Charlie is a nice guy when he's actually a serial killer). And at any rate, the sad fact is that the common man doesn't care about his "poetry of the streets" anyway. They'd most likely prefer a good wrestling picture.

The box is a metaphor for the ego - the mind. (After all, there may very well be a head inside.) The words "mind" and "head" are constantly said throughout the film. Barton has a big ego at the start of the film but by the end he realizes how naive he is. His favorite writer is even a fraud. When the woman on the beach asks what's in the box, his reply is "I don't know" and "I'm not sure." He's finally been humbled.

The photograph of this woman on the beach represents the inspiration - "the muse" - that he needs to write. (He also seeks a real muse, Judy Davis, to help him.) Once he's been through hell (some say literally) and been truly humbled - lived a little - he can finally sit down and write something real (the irony is that Hollywood doesn't want it). Now that he's enlightened, he sees things as they really are, both himself and the photograph are no longer fake. Ultimately, I think it’s the Coens smartest and funniest script. The characters are hilarious (the producer and studio head kill me) and the sound, music and cinematography are all pitch perfect. A masterpiece.